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Chemistry Alchemist
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Chloroform -> Formic Acid
I may or may not be planning on doing this reaction, im just considering what additional steps should be taken then doing this reaction AKA Heating,
reflux, distillation... this is the steps and what i think would have to be done
The first step is reacting 74.44 grams of Bleach with 58.07 grams of Acetone, this will make 119.37 Grams of Chloroform with a few by products... im
guessing you just mix them together and keep it cool to let the 2 layers separate... the Chloroform layer at the bottom and the Sodium Acetate and
Hydroxide layer up the top
NaClO + C3H6O → CHCl3 + 2 NaOH + CH3COONa
The next step is Dissolving 39.99 grams of Sodium Hydroxide in Some Ethanol and adding it to the 119.37 grams of Chloroform, This will produce 68.00
grams of Sodium Formate and 58.44 grams of Sodium Chloride. How would you separate the Sodium Chloride from the Sodium Formate?
Also, would this reaction proceed on its own or would i have to heat or reflux it for it to proceed?
CHCl3 + 4NaOH → HCOONa + 3NaCl + 2H2O
The last step once the 68.00 grams of Sodium Formate is isolated, it is then reacted with 98 grams of Sulfuric Acid, This will produce 46.02 grams of
Formic Acid along with 142.04 grams of Sodium Sulfate. Now my last question would be How would i separate the Formic Acid from the sodium Sulfate?
HCOONa + H2SO4 → CH2O2 + Na2SO4
Does this sound about right? Please do correct me if im wrong  and if this thread
belongs in Beginners and not here then feel free to move it
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francis
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I would think you would need a phase transfer catalyst, to get the hydroxide ions to react with the chloroform, wouldn't it take too long oherwise?
What is the mechanism for this reaction, how does it work?
Does the base deprotonate the chloroform to form the trichloromethyl anion?
Then what would be the next step?
[Edited on 11-10-2011 by francis]
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Chemistry Alchemist
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I wouldnt really mind if it took ages tbh haha, i wouldnt know if it needs a catalyst, i just took all the info of Wikipedia and joined it together to
form one thread, it didnn mention about catalyst but then again wiki doesnt tell everything... im not a experienced chemist, im just a guy wanting to
make things
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Picric-A
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Why not make chloroform from sodium hypochlorite + ethanol. This would give chloroform and sodium formate as a salt. The formate can be protonated to
give formic acid.
The chloroform can then be hydrolysed with NaOH and tetrabutylammonium bromide to give sodium formate and sodium chlroide. This formate can be
liekwise pronated to give formic acid.
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Chemistry Alchemist
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So doing it with ethanol would make Formic Acid in 2 parts rather then 3 as i said above? Is Sodium Sulfate soluble in formic Acid?
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Chemistry Alchemist
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NaClO + C2H6O = CHCl3 + HCOONa
I know this equation is unbalanced how what is the missing link in the reaction?
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bbartlog
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Stoichiometry is wrong. First of all, you need three moles of NaOCl per mole of acetone. Second of all, since bleach is normally sold in aqueous
solution you will need to account for that.
Also there is no point in specifying all your weights to the hundredth of a gram.
You will find if you do this with commercial bleach that the chloroform does not so much form a layer as it does a blob, i.e. you may be disappointed
at how little chloroform you get. I notice that you assume 100% yields; my yields in doing this run about 50%. I'm sure that can be improved on but if
you are planning on doing this for the first time I would not suggest assuming higher.
Anyway, there are threads on this part already.
The hydrolysis should proceed slowly even at room temperature, so heating would be needed just to make things happen more quickly. I would expect that
you can separate the formate and chloride based on the fact that the former is somewhat soluble in alcohols while the latter isn't really, but there
may be better ways.
Also, if you just want formic acid, you might look into acid decomposition of cane sugar. Would work out cheaper, I'm pretty sure.
| Quote: | | Why not make chloroform from sodium hypochlorite + ethanol. |
This doesn't proceed nearly as easily as the acetone reaction.
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Chemistry Alchemist
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I wasnt assuming 100% yeilds i was just stating the moles of each chemical... could you evaporate the bleach to form a powder and then use that
instead?
So for the Sodium Hypochlorite and ethanol, what do you mean by it doesn't proceed nearly as easily as the acetone reaction? is it much slower or are
there more steps involved?
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Retard-3000
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You'd be better of reacting the sodium chloride/sodium formate solution with HCl so you get formic acid and sodium chloride, then just distill of the
formic acid.
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Chemistry Alchemist
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Could i just evaporate the solution of Formic acid/Sodium Chloride/Water? and let the Sodium Chloride crystallize out by its own
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francis
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I think there is no benefit to using ethanol, because why add the extra steps of trying to oxidise ethanol to a ketone?
The first reaction OP mentioned presumably produces CHCl3 by the haloform reaction.
I just wonder about the second part. There's some mention of it here:
http://www.archive.org/stream/identificationof00neavrich/ide...
Also here:
http://www.books-about-california.com/Pages/Experimental_Org...
Is the idea to have (-)OH ions act as nucleophiles, substituting for the chloride ions, to form orthoformic acid, decomposing to formic acid?
In this case, since chloroform would be the solvent, how do you get the hydroxide ions to react with the chloform, since chloroform is nonpolar?
Also, how should the hydroxide preferentially act as a nucleophile, rather than a base, in the second instance deprotonating the chloroform?
To the OP:
you should try and work out moles and molarity, it will make things easier than trying to calculate reagents in grams, because some of your reagents
are liquids.
These equations you've written are useful for determining stochiometry, but only when you treat the species as moles of this, or that. This will help
you work out the limiting reagent, and the theoretical yield.
[Edited on 11-10-2011 by francis]
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bbartlog
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Quote: Originally posted by Chemistry Alchemist  | I wasnt assuming 100% yeilds i was just stating the moles of each chemical... could you evaporate the bleach to form a powder and then use that
instead?
So for the Sodium Hypochlorite and ethanol, what do you mean by it doesn't proceed nearly as easily as the acetone reaction? is it much slower or are
there more steps involved? |
You can't easily obtain solid hypochlorite by evaporation. The bleach tends to disproportionate. Also, you probably wouldn't want to. Even with 6%
bleach the reaction is fairly exothermic; with 10% bleach you need to start with ice cold reagents to avoid boiling off the chloroform as it is
formed. If you did have solid hypochlorite you would need to contain and condense the hot vapors as they formed, and probably risk an acetone fire.
So far as the ethanol reaction is concerned, I'm speaking mainly from personal experience. Ethanol plus bleach does not react much at room temperature
nor up to about 50C, and doesn't smell at all of chloroform. Maybe there is a way to do it, or I just didn't give it long enough.
| Quote: | | You'd be better of reacting the sodium chloride/sodium formate solution with HCl so you get formic acid and sodium chloride, then just distill of the
formic acid. |
It would likely be better to use a different acid. Unless you're good at titration, you won't know exactly how much HCl to use to exactly neutralize
the sodium formate. If you undershoot, you sacrifice yield; overshoot and you end up with excess HCl, which is not easily separated from the formic
acid, at least by distillation. If you use sulfuric acid you can just use a moderate excess and not worry about it distilling over with the formic
acid.
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Chemistry Alchemist
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so ur saying with the ethanol and bleach that it reacts extremely slowly at room temp? so say i left it for a week or a few weeks, do you think ill
get a reaction? or even then it may not react much?
Plus using a more concentrated acid, you will have much less water in the formic acid, you can get 98% Sulfuric Acid but you cant get 98% Hydrochloric
acid, only 32% i think
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ScienceSquirrel
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The reaction with ethanol involves initial oxidation to acetaldehyde (ethanal ) this then forms chloral ( trichloroacetaldehyde ) which cleaves to
form chloroform and formic acid.
Other side reactions eg oxidation to acetic acid take place that consumes the reagents and lowers yields.
Most inorganic reactions are A + B ---> B + C and there are no side products and yields are quantitative, losses are due to recrystallisation and
mechanical means.
Organic reactions are more like A + B ----> B + C + glop.
Often there can be more glop than product!
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Picric-A
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DO NOT use conc. sulphuric acid (>50%) to protonate the formate! This will only evolve odourless, toxic carbon monoxide and depending on the scale
will only ever result in injury, or worse still death.
Stick with hydrogen halides or phosphoric acid.
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Chemistry Alchemist
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85% phosphoric acid then?
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ThatchemistKid
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The reaction between chloroform and NaOH Intially forms the trichloromethyl anion but that quickly collapses into the dichlorocarbene I am not so sure
you can get sodium formate from that.
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bbartlog
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| Quote: Originally posted by Picric-A | DO NOT use conc. sulphuric acid (>50%) to protonate the formate! This will only evolve odourless, toxic carbon monoxide and depending on the scale
will only ever result in injury, or worse still death.
Stick with hydrogen halides or phosphoric acid. |
Who said anything about concentrated sulfuric acid? Yes, if you use enough high-test sulfuric that your final solution is >70% sulfuric acid, what
you describe would be an issue. But that can be avoided by using 35% acid (sensible here anyway) or just not adding a vast excess.
Also, if you have phosphoric acid you can obtain formic acid just by heating it with cane sugar (but be warned that what is left in the vessel will be
an awful mess).
| Quote: | | The reaction between chloroform and NaOH Intially forms the trichloromethyl anion but that quickly collapses into the dichlorocarbene I am not so sure
you can get sodium formate from that. |
Various 19th century works seem pretty confident in formate as the primary product (google books: hydrolysis chloroform formate). I seem to recall
someone here has done the reaction, too.
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Panache
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use NaHSO4 or anhydrous citric acid to liberate the formic acid, if time is not an issue, grind the two together (ie the solid acid and the
formate/NaCl mix) place into a distillation setup heat on steam bath, then leave the room for three days, voila!
edit, i have not done this, but it works for sodium acetate.
[Edited on 18-10-2011 by Panache]
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Chemistry Alchemist
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so all i have to do is get my hands on some sodium formate or another formate salt
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ScienceSquirrel
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Have a trip round the local hardware stores, etc. Some descalers are based on formic acid, usually about 40%.
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Chemistry Alchemist
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what exactly is a descaler?
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watson.fawkes
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A descaler is a commercial chemical formulation to remove Ca- and Mg-based
deposits from water high in their ions.
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ScienceSquirrel
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A descaler removes the 'fur' of insoluble salts that forms on the elements of kettles in hard water areas.
http://en.wikipedia.org/wiki/Anti-scaling_agent
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Chemistry Alchemist
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I just looked on heaps of msds's for descalers and most of the ingrediants is either Hydrochloric acid or Phosphoric acid, but then again, that could
be different to whats in the shops
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